JPS59129387A - Shell-and-tube type heat exchanger - Google Patents

Abstract

PURPOSE:To enhance efficiency in absorbing thermal stresses accompanied with a difference in thermal expansion of each pipe, by a method wherein a bellows is provided between an inner shroud provided at the outer periphery of a descending pipe in the titled heat exchanger used for a fast breeder reactor and the discending pipe, and each heat-transmitting pipe is provided with a bent part. CONSTITUTION:In a shell-and-tube type heat exchanger, a primary high-temperature fluid is passed through a heat-transmitting pipe group 4 consisting of a plurality of heat-transmitting pipes 3 provided in the interior of an outer shround 2 provided on the inside of an outer shell 1, while a secondary low-temperature fluid flows down through the descending pipe 5 vertically provided at the center of the pipe group 4, and flows up through each of the pipes 3 through a lower plenum 6, thereby exchanging heat. The difference between the thermal expansion of the group of the pipes 3 and that of the pipe 5 is absorbed by the bellows 11 provided through the inner shroud 10. Since it is considered that the stiffness of the bellows 11 is by far lower than that of the group of the pipes 3, the effect of the difference between the thermal expansion of the group of the pipes 3 and that of the pipe 5 on the bent part 12 of each of the pipes 3 is completely eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shell-and-tube heat exchanger used as an intermediate heat exchanger of a fast breeder reactor.

As shown in FIG. 1, the conventional Shell AND type heat exchanger includes an outer shell (1) suspended by a support skirt (5), an external shroud (2) inside the outer shell (1),
From a large number of heat transfer tubes (3) defined by a lower tube plate (3α) and a lower tube plate (3h) provided at the upper and lower parts of the inside of the external shroud (2), and whose upper and lower ends are fixed to these in a penetrating manner. A heat exchanger tube group part (4) in which a heat exchanger tube group is arranged, and a heat exchanger tube group part (4) vertically arranged from the upper part of the outer shell (1) to the center of the heat exchanger tube group part (4) and the upper tube plate (
3a) and the downcomer pipe (5) fixed to the upper pipe & (3b),
The lower tube plate (3 lower lower blennium (6), and the upper tube plate (3 upper upper brenum (6))
The next sieve hot side fluid is passed through the inlet nozzle (1b), the inlet window (2), descends inside the heat transfer tube group (4), passes through the outlet window (2b), and flows through the route leading to the outlet nozzle (IC). , while 2
The next low temperature side fluid flows from the inlet nozzle (5a) to the downcomer pipe (5).
It descends through the lower plenum (6), reverses itself, rises inside each heat transfer tube (3), exchanges heat, becomes high temperature, and is taken out of the equipment from the outlet nozzle (1d) through the upper plenum (7). The downcomer pipe (5) is a heat transfer pipe (
3) because it is necessary to pull it out of the outer shell (1) for repair or replacement, etc., it is connected to the upper tube plate (3a) and the lower tube plate (3b), and the upper and lower tubes of each heat transfer tube (3) are The end portions are fixed to the upper tube plate (3a) and the lower tube plate (3b) in a penetrating manner.

However, when the shell-and-tube heat exchanger is operated and the internal temperature becomes high, the temperature of each part is different, so each part has different thermal expansion, or elongation, and excessive thermal stress is generated in some parts. One example of this is the difference in thermal expansion between the heat exchanger tube (3) group and the downcomer tube (5), that is, the heat exchanger tube (3) group has a relatively high temperature and the downcomer tube (5) side has a secondary low temperature. 0111 'bij Because the temperature becomes lower depending on the body side,
A large difference in thermal expansion hj° occurs between the two, and as a result, the lower IIH is generally less rigid than the large number of heat exchanger tubes (3) group.
There is a risk that the T-tube (5) side will buckle.

In addition, a difference in thermal expansion occurs between the heat exchanger tubes (j3) forming the heat exchanger tube group, that is, as the heat exchanger becomes larger, the flow path cross section of the heat exchanger tube group (4) increases. becomes large, and uneven flow due to non-uniform flow of the primary high temperature side fluid outside each heat exchanger tube (3) tends to occur, and this uneven flow causes a difference in thermal expansion between each heat exchanger tube (3). There is a risk that certain heat transfer/'θ may be buckled.

Therefore, as a countermeasure to the above, an internal shroud is disposed around the outer periphery of the downcomer pipe (5), and one end of the internal shroud is connected to the downcomer pipe (5) via a bellows.
- The upper tube plate (3α) is connected to the inner shroud side and the lower tube plate (3A) to the downcomer pipe (5) side, respectively, so that the difference in thermal expansion between the heat transfer tube group (3) group and the downcomer pipe (5) is reduced by bellows. We have previously proposed a configuration in which the heat exchanger tubes (3) are absorbed by the heat exchanger tubes (7) caused by the uneven flow caused in the heat exchanger tube group section (4) as described above. It is not possible to absorb the mutual thermal expansion difference, and therefore heat transfer '17 (:31G
By providing a baffle inside (the flow path outside the heat transfer tube (3)) to improve the mixing properties of the fluid, it is possible to eliminate the flow by (11j!). It is not preferable to insert the panfur (1) because it increases the pressure loss and causes disadvantages such as an increase in the pump head.

In addition, as another countermeasure 7, each heat exchanger tube (3) is provided with a bent part, and the deformation of the bent part causes the difference in thermal expansion between the heat exchanger tube (3) group and the downcomer pipe (1), and the heat exchanger tube We previously proposed a configuration that absorbs the difference in thermal expansion between the heat exchanger tubes (3) that occurs due to drift in the group (4), but with this configuration, the difference in thermal expansion increases as the heat exchanger becomes larger. As a result, the protruding opening of the bent portion necessary to absorb the difference in thermal expansion between the two sides becomes larger, resulting in less flexibility and easy bending, resulting in decreased pullability and assembly, increased structural waste, and increased bending. There are various drawbacks such as difficulty in forming the parts.

The present invention was developed to eliminate the above-mentioned drawbacks of conventional shell-and-tube heat exchangers, and is a heat exchanger in which a large number of heat exchanger tubes are disposed within an external shroud inside an outer shell. The primary high-temperature fluid flows through the heat tube group, and the secondary low-temperature fluid descends in the downcomer tube installed vertically in the center of the heat transfer tube group, ascends through the lower blennium, and rises within each heat transfer tube to generate heat. In a shell-and-tube heat exchanger configured to be exchanged, an internal shroud is disposed around the outer periphery of the downcomer pipe, an end of the internal shroud is connected to the downcomer pipe via a bellows, and a group of heat transfer tubes is connected to the downcomer pipe. It is characterized by providing a bent portion in each of the heat exchanger tubes formed, and its purpose is to provide a bellows between the inner shroud provided on the outer periphery of the downcomer tube and the downcomer tube, and to bend each heat exchanger tube. A shell-and-tube heat exchanger that improves the efficiency of absorbing thermal stress caused by the difference in thermal expansion between the heat exchanger tube group and downcomer tubes and between each heat exchanger tube by combining a configuration with a bent part on the side. It is in the point of providing.

The present invention has the above-mentioned configuration, and the secondary low temperature t111
The end of the internal shroud disposed around the outer periphery of the downcomer pipe through which fluid is descended is connected to the downcomer pipe via a bellows, so the difference in thermal expansion between the heat transfer tube group and the downcomer pipe is absorbed by the bellows. If the difference in thermal expansion between the heat exchanger tubes is absorbed by the bent portion provided in each heat exchanger tube, then the rigidity of the tubes is much smaller than that of the heat exchanger tube group, so the heat exchanger tube group The thermal expansion difference between the downcomer tubes is absorbed by the rose and has no effect on the heat exchanger tube group, and the bent portion of each heat exchanger tube has a relatively small heat exchanger tube that is caused by the uneven flow within the heat exchanger tube group. Since only the mutual thermal expansion difference is applied, the deflection of the bent portion is significantly reduced, and the thermal expansion difference can be absorbed extremely efficiently.The thermal stress prevention performance is greatly improved, and the structural integrity is significantly improved. The taste is improved, and the ease of production and assembly is improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

An embodiment of the present invention is shown in FIGS. 2 and 6, in which (1) shows an outer shell suspended by a support skirt (1a), (
2) is the outer shroud arranged concentrically inside the outer shell (1), (3a) is the upper tube plate provided at the upper part of the inner side of the outer shroud (2), and (3h) is the inner side of the outer shroud (2). (3) is a large number of heat exchanger tubes whose upper and lower ends are solidly fixed to the upper and lower tube plates (3b), (4) is the heat exchanger tube ( 3) Heat exchanger tube group part where the group is arranged, (5) is the heat exchanger tube group part (π part (
4) is a descending pipe installed vertically in the center of the inner pipe, (6) is a lower pipe plate (3
b) Lower pronum formed on the lower side, (7) is the upper plenum formed on the upper tube plate (3rd upper t111), (8) is between the outer shell (1) and the lower part of the outer shell (2) The primary high-temperature side fluid flows into the outer shell (1) from the inlet nozzle (1b), and further flows into the outer shroud (2) from the inlet window (2a). After descending inside the heat exchanger tube group part (4) (outside of the heat exchanger tubes (3)), it exits from the outlet window (2h) to the outer shell (1) side and exits the outlet nozzle (
1C), and the secondary low-temperature side fluid descends from the inlet nozzle (5α) in the downcomer pipe (5), is reversed in the lower plenum (6), and ascends in each heat transfer tube (3). This is a heat exchange mechanism in which the heat is exchanged, the temperature becomes high, and it is taken out from the outlet nozzle (1d) through the upper plenum (force).

Furthermore, in this embodiment, as shown in FIGS. 2 and 6, the inner shroud (+1, 0) is arranged concentrically over substantially the entire length of the downcomer (5) with a small interval around the outer periphery of the downcomer pipe (5). The upper end of the inner shroud σα has a bellows 0υ
The lower end of the internal shroud QOI is connected to the outer periphery of the downcomer pipe (5) as necessary, and the upper tube plate (3a) The lower tube plate (3h) is fixed to the outer periphery of the downcomer pipe (5h).
) is fixed to the lower end side.

Moreover, each heat exchanger tube (3) forming the heat exchanger tube group is
As mentioned above, the upper and lower ends are connected to the upper tube plate (three and the lower tube plate).
3b) and are fixed in a penetrating manner, respectively, and
A bent portion α2 is provided at the lower part of each heat exchanger tube (3).

The illustrated embodiment has the above-mentioned configuration, and includes 1
The flow path O6 and heat exchange functions for the secondary high-temperature side fluid and the secondary low-temperature side fluid are almost the same as in the conventional example, but the heat exchanger tubes (
3) The thermal difference between the group and the downcomer pipe (5) is:
As shown in Fig. 6, it is absorbed by the pipes 01) via the internal shroud (10), and considering the rigidity of the bellows (11) and the heat transfer tube group (3), the rigidity of the R rose circle is is much smaller, so the heat exchanger tubes (3) group and the downcomer tubes (5
) has almost no effect on the bent portion 02) of each heat exchanger tube (3).

Therefore, the bent portion (12) of each heat exchanger tube (3) has a biased flow (or rl'i+
Each 1 inch heat tube (,
3) Only the mutual thermal expansion difference will be affected, and the thermal expansion that needs to be absorbed by the bent portion (12) will be extremely small.

To explain in more detail, in this example, the bending portion θ2 The displacement applied to the bellows (II) is significantly reduced, and there is no need to extremely reduce the flexibility of each heat exchanger tube (3), so the protrusion at the bent part 0 iron can be formed small, and the By arranging the 0'2 configurations in parallel, it can be applied to large-sized equipment and its structural integrity is greatly improved.

In addition, by reducing the bending of the bending part circle, the load due to contact between the heat exchanger tubes (3) and their supports is also eliminated (・ is reduced, and wear of the heat exchanger tubes is also reduced.
At the same time, compared to the case where the difference in thermal expansion is absorbed only by the bellows (11), the difference in thermal expansion between the heat exchanger tubes (3) can be absorbed by the bent portion (12), thereby preventing buckling of the heat exchanger tubes. This has the advantage of eliminating the need for a panful plate that causes drifting of currents.

1 Regarding the shape of the bent portion (12) of each heat exchanger tube (3)
When we perform the following stress evaluation and find its limit value, this evaluation is considered to be sufficiently safe for actual phenomena. An analytical model shown in Fig. 4 has been set up, and this model has validity by treating the heat exchanger tube (3) as a beam model and considering its section modulus.

The factors that determine the flexibility at the bent portion (I2) of the heat exchanger tube (3) include the protrusion It (
M), curvature of the bent part (R) and length L in the axial direction of the bent part
), and L is limited by the support position of the heat exchanger tube (3), and the heat exchanger tube support position is determined by restrictions on heat exchanger tube vibration (vibration due to fluid, earthquake resistance, etc.), so the value of L is It naturally has certain limits. Therefore, L is given as a constant value (maximum value) here.

When the axial length L) of the bent part is given as a constant value,
Since R and M are in a dependent relationship, the only parameter that affects stress for a constant displacement rate (thermal expansion measure) is considered to be only R (or only M); in other words, only R (or M only] can express the shape of the bent portion of the heat exchanger tube.

Figure 5 shows an example of the above study results, and the results are for a large heat exchanger (shell and tube type) when the effective length of the heat transfer section is 9 m.
3) Assuming that the thermal expansion difference between the group and the downcomer pipe (5) is approximately 1 CJrnm, the structural integrity of the equipment itself will not be satisfied if the bellows (11) is not provided, and in order to solve this problem, L
Either increase the value of or change the shape of the bent part to (
Countermeasures such as changing from () to (b) to make it more flexible can be considered, but all of these methods are disadvantageous as they result in reduced ease of manufacture and assembly, increased costs, and reduced structural integrity.

Although the present invention has been described above with reference to embodiments, it goes without saying that the present invention is not limited to these embodiments, and that various design modifications can be made without departing from the spirit of the invention. be.

[Brief explanation of the drawing]

Fig. 1 is a vertical sectional view showing the equipment of a conventional shell-and-tube heat exchanger, Fig. 2 is a longitudinal sectional view showing the mechanism of an embodiment of the present invention, and Fig. 6 is an enlarged view of the main parts of Fig. 2. 4 is an analytical model diagram of the shape of the bent portion of the heat exchanger tube, FIG. 5 is a diagram showing the results of an examination of the shape of the bent portion of the heat exchanger tube, and FIG. 6 is a diagram of a measure to improve the flexibility of the bent portion. 1: External 2: External shroud 6: Heat exchanger tube 31Z,
31! l: Upper and lower tube plates 4: Heat exchanger tube group section 5: Downcomer tube 6: Lower plenum 7: Upper plenum 10: Internal shroud 11: Bellows 12: Bend section sub-agent Patent attorney Shige Okamoto 2nd person 1st M Pen Figure 2

Claims (1)

[Scope of Claims] The primary high temperature side fluid flows 1rTh into the heat transfer tube group section in which a large number of heat transfer tubes are arranged in the external shroud inside the outer shell, and the secondary low temperature side fluid flows into the AC heat transfer tube group section. In a shell-and-tube type heat exchanger, heat exchange is performed by descending in a downcomer pipe vertically installed in the center of the heat exchanger and ascending in each of the heat transfer tubes via a lower plenum. An internal shroud is disposed around the outer circumference of the downcomer pipe, and the internal shroud
1) A shell-and-tube type heat exchanger characterized in that each of the heat transfer tubes forming a group of heat transfer tubes is provided with a bent portion while being connected to the downcomer tube of 1) No. 11 through a bellows at the end of the tube. vessel.